Vacuum-Assisted Assembly of Aramid Nanofiber/Hydroxyapatite Composite Films: Mechanical Reinforcement and Significant Insulation Enhancement via Hot Pressing

High-performance electrical insulating materials are critical for ensuring the safe and reliable operation of electrical equipment under high-voltage and high-integration conditions. In this study, aramid nanofiber (ANF)/hydroxyapatite (HAP) composite films were fabricated via a vacuum-assisted filtration process, combined with hot pressing. The results demonstrate that the incorporation of 10 wt % HAP enables the composite film to achieve a tensile strength of 155.8 MPa and a breakdown strength of 43.2 kV/mm, representing increases of 43.1% and 21.7%, respectively, compared to those of the pristine ANF film (108.9 MPa, 35.5 kV/mm). After hot pressing, the composite film with 30 wt % HAP exhibits a breakdown strength of 203.5 kV/mm, which is 80.4% higher than that of the hot-pressed pristine ANF film (112.8 kV/mm) and markedly 498.5% higher than that of its nonhot-pressed counterpart (34.0 kV/mm). Microstructural analysis reveals that hot pressing promotes the formation of a dense laminated structure within the film, which helps to suppress the propagation of the breakdown paths. This strategy provides a facile and effective route for the preparation of high-performance, insulating materials.